Electronically commutated motors, or brushless motors, are useful for a variety of applications. These applications include Heating/Ventilation/Air Conditioning (HVAC) blowers, consumer appliances, pumps, cooling fans in electronic equipment, and cordless power tools.
Nevertheless, designing control systems for such brushless motors presents a number of challenges. Brushless motors are typically electronically commutated using control systems employing feedback from position sensors (e.g. magnetic Hall sensors). These position sensors, however, do not indicate correct commutation times due to of a variety of factors. These factors include imprecise mounting of the position sensors due to limited available space, hysteresis output from the sensor itself, and imperfections in the sensor manufacturing process. The inaccurate commutation points that result can cause imbalanced phase conduction, torque ripples, and reduced power efficiency. Furthermore, because many brushless motors are configured to generate a sinusoidal back-Electromotive Force (EMF) during operation, sinusoidal-weighted control is desirable to provide smoother and more precise control for such motors, especially at low speeds. However, generating sinusoidal-weighted motor control signals requires higher resolution and more highly adaptive dynamic control than that which is provided by typical digital-output implementations of position sensors.